Galileo's Lunar Crater: The Story of a Misplaced Confession
Galileo Galilei was one of the first people to study the Moon using a telescope. You would think he would be able to get a hole more than 10 miles wide for his efforts. But of course, there are more details.
Close-up of the Moon's surface, showing a crater with the caption: "Crater Galileo (arrow) near a feature called Rainer Gamma (bright oval) as seen in the 1651 book "Almagestum Novum" by astronomer Giovanni North. The crater is named Battista Riccioli after the famous astronomer Galileo North.
Galileo is a small, symmetrical crater with a sharp edge, located near Reiner Gamma in the western Ocean of Storms.
Galileo A and B are two satellite craters located to the north and west of Galileo.
Galilei Valley is a narrow valley that can be viewed using a modest telescope.
The Marius Hills is a large field of volcanic domes containing over 250 strange conical hills.
Lunar Observations / LRO
Glance at the full moon, and you'll see names like Kepler, Copernicus, and Tycho scattered across the scene like billboards on a highway. But where is Galileo? Although he was not the first to observe the Moon using a telescope—that honor goes to Thomas Harriot of England—Galileo was the first to record and report on lunar craters, discover Jupiter's four largest moons, observe the phases of Venus, and discern the stellar nature of the Trail Galaxy. Milky Way. He certainly deserves a monument no less than the other greats.
Image: A telescopic image of the lunar surface showing the Galileo Crater. The caption reads: "Galileo Crater first appears two or three days before the full Moon and remains visible for about 10 days afterward. The crater is best seen near the terminator, which will occur on June 3 and 4 and again on June 19 and 20. North is up."
Bob King
Oh, it’s there, but I suspect few of us have stopped by. You’ll find the unremarkable 16-kilometer-wide (10-mile-wide) Galileo Crater in western Oceanus Procellarum near Reiner Gamma, a swirling magnetic anomaly that played a key role in the crater’s mysterious story. The area also hosts Marius Hills, the largest volcanic dome field on the Moon, with more than 250 strange conical mounds. When viewed in the slanted sunlight near the boundary, they resemble an outbreak of beehives.
Image: A close-up image of the Reiner Gamma feature on the Moon, showing an oval shape with the caption: "Italian astronomer Giovanni Riccioli assigned Galileo Crater (arrow) to the bright oval shape we know today as Reiner Gamma. The astronomer also named the craters alongside (circled) for himself and mapmaker Francesco Grimaldi. North is up."
Giovanni Riccioli
Galileo first appeared on a map drawn by Francesco Maria Grimaldi and published in the book "Almagestum Novum" by astronomer Giovanni Battista Riccioli in 1651. Riccioli used his former student’s map to introduce a lunar naming system that became the basis for our modern naming scheme. Craters carried Latin names of famous scientists and philosophers, while lunar "seas" received names related to water like Mare Imbrium (Sea of Rains) or states of mind like Mare Tranquillitatis (Sea of Tranquility). Moreover, craters in the Moon’s northern hemisphere honored prominent figures from the ancient world while Riccioli named those in the south after his contemporaries.
Image: A NASA Lunar Reconnaissance Orbiter image of Reiner Gamma, with a caption that reads: "NASA's Lunar Reconnaissance Orbiter captured this close-up image of the Reiner Gamma oval shape, formerly called Galileo."
Grimaldi interpreted the bright, prominent oval shape of Reiner Gamma as a volcanic crater—that was the state of the art at the time—and Riccioli felt obliged to call it Galileo in honor of the great astronomer. In reality, the feature has no depth whatsoever. It is the largest of many lunar swirls, areas where strong, localized magnetic fields—tiny magnetic fields, if you will—deflect the solar wind and maintain the bright tone of the lunar regolith.
Galileo remained in the sights of telescopic observers for over 180 years until the publication of Mappa selenographica, a wonderfully detailed lunar map in four quadrants compiled by German astronomers Wilhelm Beer and Johann Heinrich Mädler. When the four sections were put together, each one stretched nearly a meter across .
On Johann Madler's selenographic map published in 1834. Reiner gamma is the bright patch called gamma (γ) to the upper left of the crater. The south is down.”
Mädler introduced some changes to Riccioli’s naming system. In his map, only prominent lunar craters carried names; smaller craters near primary craters were identified with letters. For example, Kepler is accompanied by lunar craters Kepler A, Kepler B, and so on. Other features like domes, mountain peaks, or, in the case of Reiner Gamma, bright white patches were designated with Greek letters. By the telescopes of the 19th century, it was clear that Grimaldi’s Galileo wasn’t a crater. So Mädler selected the largest unnamed crater near the Reiner Gamma oval and named it Galileo. Pluto is shaking his head knowingly right now.
Telescopic view of Galileo Crater and a nearby comet. The caption reads: "I photographed Comet Galileo and Moon Crater A at sunrise using a mobile phone and a 10-inch Dobsonian telescope on May 20, 2024. They formed a striking pair in dim light. Passing through are several north-south oriented wrinkly hills, formed during the disturbance Crusts called thrust faults, across the Oceanus Procellarum in the vicinity of the craters.”
We must always remember to keep things in perspective. Thomas Harriot, long dead, had to wait until 1970 to land on the moon. Although it is 56 kilometers (35 miles) across, it is located on the far side of the Moon, making it out of reach of almost all observers. Although Galileo Crater may not be particularly noticeable on its own, the site is rich in excellent observing targets that include volcanic domes, jagged canyons, wrinkled ridges, and magnetic mysteries.
But don't feel too sad for Galileo. The Italian astronomer caused the biggest stir on Mars. The Galileo crater on Mars is 137 kilometers (85 miles) in diameter, which is even larger than the nearby Tycho crater on the moon.
Add information about the moon split:
The splitting of the moon is an important event mentioned in the Holy Qur’an (54:1): “The Hour has approached and the moon has split.” This miraculous event, which occurred during the time of the Prophet Muhammad (may God bless him and grant him peace), serves as a testimony to the power of God. He was a sign for those who disbelieved in the Prophet's message, and he still arouses awe and wonder among believers.
Although there is no direct hadith (sayings of the Prophet) describing how the moon split, the Qur’anic verse is a powerful reminder of God’s ability to change the laws of nature for His purposes.
This event, along with other miracles, helps strengthen faith and understanding of the divine.